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Application of Fractal Theory in Simulation of Ferromagnetic Elements' Hysteresis loop in Transformer

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Journal of Beijing Institute of Technology 2003年第2期12卷 113-118页

作者：毕军付梦印张宇河 Department of Automatic Control

The simulation of the transformer transient is one of the indispensable qualifications for improving the performance of transformer protection, the key technique of the transformer's transient simulation is the treatment of ferromagnetic elements' loop. Thus the shapes of the primary Hysteresis loop and each internal secondary Hysteresis loop in the identical magnetism conducting are analyzed, and then it is proposed that there are some fractal characteristics in the relation between them. The fractal phenomenon of the ferromagnetic elements' Hysteresis loop in the transformer's transient simulation is first brought forward, the mutuality between the ferromagnetic elements' primary Hysteresis loop and its secondary Hysteresis loops is revealed in mechanism by using the fractal theory. According to the iterated function system of fractal theory, the secondary Hysteresis loops can be generated by the iterative calculation of the primary loop. The simulation results show the validity of this idea.

关键词： fractal theory Hysteresis loop transformer simulation

Oblique shock train motion based on schlieren image processing

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Chinese Journal of Aeronautics 2023年第3期36卷 30-41页

作者： Longsheng XUE Chuan CHENG Chengpeng WANG Lantian ZHANG Kang LI Keming CHENG College of Aerospace Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China Key Laboratory of Unsteady Aerodynamics and Flow Control Ministry of Industry and Information TechnologyNanjing University of Aeronautics and AstronauticsNanjing 210016China Beijing Institute of Tracking and Telecommunication Technology Beijing 100094China Aerospace System Engineering Shanghai Shanghai 201109China

In this paper,shock train motion in a Mach number 2.7 duct is studied experimentally,and large numbers of schlieren images are obtained by a high-speed camera.An image processing method based on Maximum Correlation Detection(MCD)is proposed to detect shock train motion from the schlieren images,based on which the key structures,e.g.,separation positions and separation shock angles on the top and bottom walls,can be analysed in detail.The oscillations of the shock train are generated by rhombus and ellipse shafts at various excitation frequencies.According to the analysis of MCD results,the distributions of the frequency components of shock train oscillation generated by the two shafts are distinctly different,in which the motion generated by the ellipse shaft is much smoother;shock train motion is mainly characterized by the oscillation of separation position while the separation shock strength is not so sensitive to downstream disturbance;there is a Hysteresis loop relation between the downstream pressure and separation position.

关键词： Frequency components Hysteresis loop Maximum Correlation Detection(MCD) Schlieren image processing Shock train oscillation

Estimation of critical current density of bulk superconductor with artificial neural network

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Superconductivity 2023年第3期7卷 34-45页

作者： Gangling Wu Huadong Yong Key Laboratory of Mechanics on Disaster and Environment in Western China The Ministry of Education of ChinaLanzhou UniversityLanzhouGansu 730000People’s Republic of China Department of Mechanics and Engineering Sciences College of Civil Engineering and MechanicsLanzhou UniversityLanzhouGansu 730000People’s Republic of China

In the applications of superconducting materials,the critical current density J_(c)(B)is a crucial performance parameter.The conventional method of measuring J_(c)(B)of bulk superconductor is magnetization method.However,there are errors in the estimation of J_(c)(B)in the lower field,and the estimation is not applicable in the region where the magnetic field reverses.In this paper,J_(c)(B)of the bulk superconductor is determined by the hysteresis and magnetostriction loops with artificial neural network(ANN),respectively.Compared with double‐output ANN,the critical current density obtained by single‐output ANN is more accurate.Finally,the prediction results given by the hysteresis and magnetostriction loops are discussed.

关键词： Critical current density ANN Kim model Hysteresis loop Magnetostriction loop Bulk superconductor

Supersonic flow over a pitching delta wing using surface pressure measurements and numerical simulations

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Chinese Journal of Aeronautics 2018年第1期31卷 65-78页

作者： Mostafa HADIDOOLABI Hossein ANSARIAN Aerospace Engineering Department Malek Ashtar University of Technology

Experimental and numerical methods were applied to investigating high subsonic and supersonic flows over a 60°swept delta wing in fixed state and pitching oscillation. Static pressure coefficient distributions over the wing leeward surface and the Hysteresis loops of pressure coefficient versus angle of attack at the sensor locations were obtained by wind tunnel tests. Similar results were obtained by numerical simulations which agreed well with the experiments. Flow structure around the wing was also demonstrated by the numerical simulation. Effects of Mach number and angle of attack on pressure distribution curves in static tests were investigated. Effects of various oscillation parameters including Mach number, mean angle of attack, pitching amplitude and frequency on Hysteresis loops were investigated in dynamic tests and the associated physical mechanisms were discussed. Vortex breakdown phenomenon over the wing was identified at high angles of attack using the pressure coefficient curves and Hysteresis loops, and its effects on the flow features were discussed.

关键词： Delta wing Hysteresis loop Pitching oscillation Supersonic flow Vortex breakdown

Study on the thixotropy and structural recovery characteristics of waxy crude oil emulsion

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Petroleum Science 2021年第4期18卷 1195-1202页

作者： Li-Ping Guo Xue Han Yun Lei Lei Wang Peng-Fei Yu Shuang Shia Key Laboratory of Enhanced Oil Recovery Ministry of EducationNortheast Petroleum UniversityHeilongjiang163000China Jiangsu Key Laboratory of Oil and Gas Storage&Transportation Technology Changzhou UniversityJiangsu213164China Exploration and Development Research Institute Daqing Oil Field Company LtdDaqingHeilongjiang163712China

Waxy crude oil emulsion has thixotropic properties at the temperature near gel point,which is a macromechanical characterization of the structure failure and recovery of waxy crude oil emulsion.In this paper,the thixotropic behaviors of waxy crude oil emulsion near gel point were studied using Hysteresis loop formed by stress linear increase and decrease,as well as the structural recovery characteristics.The influence of the loading conditions and water content on the thixotropy of waxy crude oil emulsion were analyzed with Hysteresis loop area.The concept of"structural recovery"was introduced to study the degree of structural recovery after different stewing,and influencing factors were taken into account.Results have shown that for waxy crude oil emulsion,the failure to fully restore of the structure after lysis is the cause of the formation of Hysteresis loop,and the loading conditions will not affect the strength of thixotropy and the degree of structural recovery.Additionally,the dispersed phase droplets weaken the thixotropy and structure recovery characteristics of waxy crude oil emulsion,and the greater the water content,the weaker the thixotropy.The findings can help to better understand the safe and economic operation of waxy crude oil-water pipeline transportation.

关键词： Waxy crude oil Emulsion Thixotropic properties Structural recovery Hysteresis loop

Strain Amplitude Effect on the Viscoelastic Mechanics of Chloroprene Rubber

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Acta Mechanica Solida Sinica 2020年第3期33卷 392-402页

作者： Longfan Peng Zhida Li Yunyu Li Institute of Transportation Wuhan University of TechnologyWuhan 430063HubeiChina

This paper establishes an empirical formula to predict the strain amplitude effect.A viscoelastic constitutive model-the superposition of a hyperelastic model and a viscoelastic model-is constructed based on the laws of thermodynamics.The Mooney Rivlin model and the Prony series are employed for uniaxial tension testing.The empirical formula is derived using a Hysteresis loop;it obtains results that are in agreement with the experimental results of dynamic mechanical analysis(DMA).The empirical formula proposed in this paper has certain accuracy in predicting the dynamic modulus under different strain amplitudes.

关键词： Viscoelasticity Strain amplitude effect Storage modulus Loss modulus Hysteresis loop

An experimental study of in-plane arch-shaped dampers

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Earthquake Engineering and Engineering Vibration 2018年第4期17卷 849-867页

作者： Chien-Liang Lee Yen-Po Wang Meng-Yan Cai School of Civil Engineering and Architecture Xiamen University of Technology Xiamen 361024 Fujian China Department of Civil Engineering Chiao-Tung University Hsinchu 30010 Chinese Taipei

As an effort to minimize material utilization, seismic steel dampers designed to deform inelastically in an in-plane flexural mode have attracted serious attention recently. This paper presents a new type of metallic yielding damper referred to as the in-plane arch-shaped damper modified from its portal frame-shaped counterpart by replacing the straight beam with a circular arch to minimize the effects of stress concentration and warping, and therefore to avoid premature failure. Component tests of both the portal frame-shaped and arch-shaped in-plane dampers were conducted for comparison. Hysteresis loops obtained from the component tests under cyclic loads indicate substantial improvement on the energydissipative characteristics of the proposed damper. Moreover, seismic performance assessment of the proposed damper was carried out further via shaking table tests of a five-story model frame. Encouraging results have been achieved in terms of acceleration reduction, damping enhancement and peak suppression of the frequency response functions, suggesting the potential of the proposed device to be used in earthquake-resisting systems.

关键词： seismic metallic yielding damper in-plane arch-shaped damper Hysteresis loop shaking table test

Prediction of flexoelectricity in BaTiO_(3) using molecular dynamics simulations

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Chinese Physics B 2023年第1期32卷 530-538页

作者：周龙张旭龙曹玉莹郑富高华刘红飞马治 School of Physics and Electronic-Electrical Engineering Ningxia UniversityYinchuan 750021China State Key Laboratory of High-Efficiency Utilization of Coal and Green Chemical Engineering Ningxia UniversityYinchuan 750021China

Flexoelectric effect, referring to the strain gradient induced polarization, widely exists in dielectric materials, but its molecular dynamics has not been studied so much so far. In this work, the radial distribution function of BaTiO_(3) and the phase transition temperatures have been investigated, and the results show that the core-shell potential model is effective and the structure of BaTiO_(3) is stable in a temperature range of 10 K–150 K. Molecular dynamics simulated Hysteresis loops of BaTiO_(3) show that anisotropy can play an important role in the coercive field. Based on the rational simulation process,the effects of cantilever beam bent angle and fixed length on the polarization are analyzed. It is found that the small bent angle of the curved cantilever beam can give a proportional relationship with a fixed end length and a non-linear relationship is presented when the bent angle is much larger. The prediction of flexoelectric coefficient in BaTiO_(3) is 18.5 nC/m. This work provides a computational framework for the study of flexoelectric effect by using molecular dynamics.

关键词： flexoelectric effect molecular dynamics phase transition Hysteresis loop

Energy dissipation of a ring-like metal rubber isolator

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Chinese Physics B 2014年第4期23卷 198-201页

作者：闫辉张文静姜洪源陈亮 School of Mechatronics Engineering Harbin Institute of Technology

Metal rubber （MR） is a kind of homogeneous poroelastic damping material made of metal wire. In this paper, by ana- lyzing the forces on the MR isolator and the MR element, the Hysteresis loops of the force and deformation are studied and verified by experiments. The results show that the force and displacement Hysteresis loop of the MR isolator is described by the force and deformation Hysteresis loops of the MR elements. In addition, the relationship between the energy dissipation coefficient of the MR element and that of the MR isolator is derived. The energy dissipation coefficient is programmed and calculated by MATLAB using experimental data, and the results are compared with the theoretical value. It is the basis for the design and applied research of the MR isolator in a future study.

关键词： metal rubber Hysteresis loop experimental study energy dissipation coefficient